Series modulation system employing fluid cooled thermionic valves



Patented Mar. '17, 1936 SEREES MODULATION SYSTEM EMPLOYING FLUID COOLED THERBHONIC VALVES lhornas Henry Price, Chelmsford, England, assignor to Radio Corporation of America, a corporation of Delaware Application July 1, 1933, Serial No. 678,580 In Great Britain July 7, 1932 Claims.

This invention relates to modulation arrangements employing fluid cooled thermionic valves and more specifically to so-called series modulation systems wherein the modulation valve or 5 valves and the high frequency valve or valves in which modulation is effected have their anodes cooled by a fluid cooling system, e. g., a water cooling system.

In the well known series modulation arrangement the modulation valve is connected in series with and on the low potential side of the high frequency valve and the applied voltage is connected right across the two valves. As is obvious, full modulation will only be obtainable in this 5 arrangement if all the current going through the high frequency valve also passes through the modulation valve. Now, in many cases both the high frequency valve and the modulation valve have water or other fluid cooled anodes and 20 therefore in such cases, the fluid supply systems for cooling the valves will constitute resistive connections between earth and the two anodes, i. e., in the ordinary arrangement employing fluid cooled valves, the fluid supply systems electrically 25 constitute resistances in shunt between earth and the two valve anodes. The effect of connecting a resistance in shunt across the modulation valve introduces slight distortion since the resistance of the said modulation valve will vary in accordance 30 with the modulating potentials applied thereto, whereas the resistance in shunt with this valve will not vary in this manner.

The present invention has for its object to avoid the above mentioned disadvantage.

35 According to this invention in a series modulation system employing fluid cooled valves, the cooling fluid supply and outlet pipes of the modulation valve are connected to a point at a higher electrical potential than that of the modulation valve anode.

The novel features of this invention will be more clearly understood by referring to the accompanying drawing, in which, 7

Fig. 1 shows a well-known modulation method as mentioned above, the high frequency valve being represented by a rectangle A, and the modulation valve being represented by a rectangle B, both having connected therewith high potential terminals +HT and -HT. The characters R1 and R2 represent the fluid supply resistance.

Fig. 2 shows an arrangement similar to Fig. 1

except for the incorporation of the features of this invention. 55 Fig. 3 shows a more detailed arrangement of this invention and is generally similar to that of Fig. 2.

The invention may be carried into effect in various different ways. For example, the supply and outlet pipes of the modulation valve may be 5 connected respectively to T fittings 8 and [0 near the anode ends of the supply and outlet pipes l2 and M, respectively, of the high frequency or oscillator valve. This results in an arrangement which is schematically represented 10 in Figure 2, from which it will be seen that the resistance R2, due to the fluid cooling system, which was previously connected between the anode of the valve at B and as shown in Fig. 1, is now connected between the anode of the valve at B and the anode of the valve at A. The nature of the connections is shown more clearly in Figure 3. The advantage of the invention may be Obtained by metallically and directly connecting points in the supply and outlet pipes of the modulator valve to any point of higher electrical potential than the potential of the said modulator valve anode.

Having thus described my invention and the operation thereof, what I claim is: 1. A modulation system comprising a plurality of fluid cooled anode valves, a fluid cooling system, one of said valves serving as a modulation valve, another one of said valves serving as a high frequency valve, a source of anode potential, means connecting said modulation and high frequency valves and said source of anode potential in series, and a connection from said source to said fluid cooling system for maintaining said cooling system at a higher electrical potential than the anode of said modulating valve.

2. A series modulation system comprising a plurality of fluid cooled anode valves, at least one of said valves serving as a modulation valve, and at least another of said valves serving as a high frequency valve, a fluid cooling system for said anodes, a source of anode potential, means connecting said modulation and high frequency valves and said source of anode potential in series, an outlet for cooling said system, said outlet being connected at a higher electrical potential than the anode of said modulating valve.

3. A series modulation system comprising a plurality of fluid cooled anode valves, at least one of said valves serving as a modulation valve and at least another of said valves serving as a high frequency valve, a fluid cooling system for said anodes, a source of anode potential, means connecting said modulating and high frequency valves and said source of anode potential in series, said modulating valve having branched supply and outlet pipes and means for connecting said supply and outlet pipes at a higher electrical potential than the anode of said modulating valve.

4. A series modulation system comprising a plurality of fluid cooled anode valves, at least one of said valves serving as a modulation valve and at least another of said valves serving as a high frequency valve, a fluid cooling system for said anodes, a source of anode potential, means connecting said modulating and high frequency valves and said source of anode potential in series, said modulating valve having branched supply and outlet pipes with T fittings and means to provide an outlet pipe from the high frequency valve With a point of higher electrical potential than the anode of said modulating valve.

5. High frequency apparatus comprising a high frequency valve having an anode, a modulator valve having an anode, a source of anode potential, means connecting said valves and source in series, a liquid cooling system for the anode of said. modulator valve, a connection from said source to said liquid cooling system maintaining said system at a potential higher than the anode of said modulator valve whereby the resistance of said cooling system is prevented from efiectively acting in shunt to the anode circuit of said modulator valve.

THOMAS HENRY PRICE. 

